One surgeon's learning curve with single position lateral lumbar interbody fusion: perioperative outcomes and complications

Learning curve analyses in spine surgery: a systematic simulation-based critique of methodologies

BACKGROUND CONTEXT

Various statistical approaches exist to delineate learning curves in spine surgery. Techniques range from dividing cases into intervals for metric comparison, to employing regression and cumulative summation (CUSUM) analyses. However, their inherent inconsistencies and methodological flaws limit their comparability and reliability.

PURPOSE

To critically evaluate the methodologies used in existing literature for studying learning curves in spine surgery and to provide recommendations for future research.

STUDY DESIGN

Systematic literature review.

METHODS

A comprehensive literature search was conducted using PubMed, Embase, and Scopus databases, covering articles from January 2010 to September 2023. For inclusion, articles had to evaluate the change in a metric of performance during human spine surgery across time/a case series. Results had to be reported in sufficient detail to allow for evaluation of individual performance rather than group/institutional performance. Articles were excluded if they included cadaveric/nonhuman subjects, aggregated performance data or no way to infer change across a number of cases. Risk of bias was assessed using the Risk of Bias in Nonrandomized Studies of Interventions (ROBINS-I) tool. Surgical data were simulated using Python 3 and then examined via multiple commonly used analytic approaches including division into consecutive intervals, regression and CUSUM techniques. Results were qualitatively assessed to determine the effectiveness and limitations of each approach in depicting a learning curve.

RESULTS

About 113 studies met inclusion criteria. The majority of the studies were retrospective and evaluated a single-surgeon's experience. Methods varied considerably, with 66 studies using a single proficiency metric and 47 using more than 1. Operating time was the most commonly used metric. Interval division was the simplest and most commonly used method yet inherent limitations prevent collective synthesis. Regression may accurately describe the learning curve but in practice is hampered by sample size and model choice. CUSUM analyses are of widely varying quality with some being fundamentally flawed and widely misinterpreted however, others provide a reliable view of the learning process.

CONCLUSION

There is considerable variation in the quality of existing studies on learning curves in spine surgery. CUSUM analyses, when correctly applied, offer the most reliable estimates. To improve the validity and comparability of future studies, adherence to methodological guidelines is crucial. Multiple or composite performance metrics are necessary for a holistic understanding of the learning process.

Single-position oblique lumbar interbody fusion with navigation: improved efficiency and screw accuracy compared to dual-position with fluoroscopy

Dual-position oblique lumbar interbody fusion with fluoroscopy (D-OLIF) requires repositioning the patient to a prone position for pedicle screw insertion. Recently, single-position surgery with navigation has been introduced. However, there are concerns regarding pedicle screw accuracy and achieving appropriate sagittal balance in single-position OLIF with navigation (S-OLIF). The purpose of this study is to evaluate the clinical and radiological outcomes of S-OLIF compared to D-OLIF. A retrospective analysis was conducted on 102 patients who underwent single-level OLIF at a single institution. The patients were divided into two groups: 55 in the S-OLIF group and 47 in the D-OLIF group. The numeric rating scale for back and leg, Oswestry disability index, and walking distance improvements showed no significant difference. However, the EuroQol 5-dimension 5-level index showed higher improvement in the S-OLIF (P = 0.029). The segmental lordosis, lumbar lordosis, and C7 sagittal vertical axis showed no significant difference. S-OLIF had significantly fewer cases of pedicle screw malposition (P = 0.045). Additionally, the surgery time was shorter in the S-OLIF (P = 0.002). In conclusion, S-OLIF exhibited clinical and radiological outcomes comparable to D-OLIF, with the added advantages of reduced surgery time and enhanced accuracy in pedicle screw placement.

Biomechanical Comparison of Unilateral and Bilateral Pedicle Screw Fixation after Multilevel Lumbar Lateral Interbody Fusion

STUDY DESIGN

Human Cadaveric Biomechanical Study.

OBJECTIVES

Lumbar Lateral Interbody Fusion (LLIF) utilizing a wide cage has been reported as having favorable biomechanical characteristics. We examine the biomechanical stability of unilateral pedicle screw and rod fixation after multilevel LLIF utilizing 26 mm wide cages compared to bilateral fixation.

METHODS

Eight human cadaveric specimens of L1-L5 were included. Specimens were attached to a universal testing machine (MTS 30/G). Three-dimensional specimen range of motion (ROM) was recorded using an optical motion-tracking device. Specimens were tested in 3 conditions: 1) intact, 2) L1-L5 LLIF (4 levels) with unilateral rod, 3) L1-L5 LLIF with bilateral rods.

RESULTS

From the intact condition, LLIF with unilateral rod decreased flexion-extension by 77%, lateral bending by 53%, and axial rotation by 26%. In LLIF with bilateral rods, flexion-extension decreased by 83%, lateral bending by 64%, and axial rotation by 34%. Comparing unilateral and bilateral fixation, LLIF with bilateral rods reduced ROM by a further 23% in flexion-extension, 25% in lateral bending, and 11% in axial rotation. The difference was statistically significant in flexion-extension and lateral bending (P < .005).

CONCLUSIONS

Considerable decreases in ROM were observed after multilevel (4-level) LLIF utilizing 26 mm cages supplemented with both unilateral and bilateral pedicle screws and rods. The addition of bilateral fixation provides a 10-25% additional decrease in ROM. These results can inform surgeons of the incremental biomechanical benefit when considering unilateral or bilateral posterior fixation after multilevel LLIF.

The Utility and Appropriateness of Single-Position Circumferential Lumbar Interbody Fusion Using O-Arm-Based Navigation in the Novel Oblique Position

PURPOSE

Single-position surgery with patients in a lateral position, which involves inserting percutaneous pedicular screws (PPS) and lateral interbody fusion (LIF) to avoid changing the position, has been reported. The purpose of the present study was to evaluate the utility and appropriateness of single-position LIF-PPS using O-arm-based navigation in the innovative oblique position.

METHODS

This study involved a retrospective analysis of 92 consecutive patients with lumbar spondylolisthesis who underwent LIF-PPS using O-arm-based navigation. Thirty-five subjects demonstrated surgery with repositioning, as well as 24 in the lateral decubitus position, and 33 in the oblique during PPS, where the position was changed to the lateral decubitus position using bed rotation without resetting. We compared these three groups in terms of the surgery time, blood loss, and the accuracy of the screw placement.

RESULTS

The operative time was significantly shorter in the single-position surgery, both in the lateral and oblique positions, compared to surgery in a dual position. The blood loss was significantly increased in the lateral position compared to the dual and oblique positions. The screw trajectory angle on the downside was significantly smaller in the lateral position, and the accuracy of the screw placement on the downside was significantly lower in the lateral position compared to the dual and oblique positions.

CONCLUSION

Single-position surgery could reduce the average surgery time by about 60 min. The present study indicated the oblique position during PPS insertion might make single-position surgery more useful to improve the accuracy of PPS on the downside, with less blood loss.

Advanced Age Does Not Impact Outcomes After 1-level or 2-level Lateral Lumbar Interbody Fusion

STUDY DESIGN

This was a retrospective comparative study.

OBJECTIVE

The objective of this study was to assess the effect of increased age on perioperative and postoperative complication rates, reoperation rates, and patient-reported pain and disability scores after lateral lumbar interbody fusion (LLIF).

SUMMARY OF BACKGROUND DATA

LLIF was developed to minimize soft tissue trauma and reduce the risk of vascular injury; however, there is little evidence regarding the effect of advanced age on outcomes of LLIF.

METHODS

Patients who underwent LLIF from 2009 to 2019 at one institution with a minimum 6-month follow-up were retrospectively reviewed. Patients less than 18 years old with musculoskeletal tumor or trauma were excluded. The primary outcome was the preoperative to postoperative change in the Numeric Pain Rating Scale (NPRS) for back pain. Operative time, estimated blood loss, length of stay, perioperative and 90-day complications, unplanned readmissions, reoperations, and change in Oswestry Disability Index were also evaluated. Relationships with age were assessed both with age as a continuous variable and segmenting by age below 70 versus 70+.

RESULTS

In total, 279 patients were included. The median age was 65±13 years and 159 (57%) were female. Age was not related to improvements in back NPRS and Oswestry Disability Index. Operative time, estimated blood loss, length of stay, perioperative and 90-day complications, unplanned readmissions, reoperations, and radiographic fusion rate also were not related to age. After multivariable risk adjustment, increasing age was associated with greater improvements in back NPRS. The decrease in back NPRS was 0.68 (95% confidence interval: 0.14, 1.22; P=0.014) points greater for every 10-year increase in age. Age was not associated with rates of complication, readmission, or reoperation.

CONCLUSIONS

LLIF is a safe and effective procedure in the elderly population. Advanced age is associated with larger improvements in preoperative back pain. Surgeons should consider the benefits of LLIF and other minimally invasive techniques when evaluating elderly candidates for lumbar fusion.

LEVEL OF EVIDENCE

Level III.